Metal working



Oct. 11, 1966 c. L. sPoRcK METAL WORKING Filed Oct. 5, 1963 INV NTOR ATTORNEY United States atent 3,277,683 Patented Oct. 11, 1966 ice Fiied Oct. 3, 1963, Ser. No. 313,649 6 Claims. c1. 72-368) This invention relates to metal working and in particular relates to methods for making hollow, geometric forms, for example, metal objects having tubular, conical or bowl shaped forms.

Typical parts having the forms mentioned are, for example, tubualr shapes used as starting blanks in tube forming operations, closed-end cylinders adapted to hold industrial gases and bowl shaped parts utilized as truck wheels.

In its preferred form, the invention contemplates a rolling operation on a cylindrically shaped blank, the rolling operation being performed by means of a pair of rollers each making a line contact with one end of the blank and then effecting relative motion between the blank and the rollers so that the rollers exert a force and roll around the end and cause the end to yield and flow outwardly. The flowed metal is then engaged and guided into a desired geometric form, for example, into the form of a cylinder, a cone or a bowl. In most instances, the forming operation is carried out on a hot blank.

One advantage of the invention is that relatively small forces are needed for the flow process and hence the equipment can be small and inexpensive.

Another advantage is that the flowing can be done relatively rapidly while holding the dimensions of the formed article well wit-bin acceptable commercial tolerances.

A particularly important feature of the invention is that it eliminates the disadvantages of the techniques which are conventionaly used to make articles of the kind in question, for example, the excessive die wear of extrusion presses and the waste of material associated with machining.

The invention will be explained below in connection with the following drawings wherein:

FIGURE 1 is an elevational view partially in section illustrating a type of equipment for practicing the invention;

FIGURE 2 is a diagrammatic view of certain principles of the invention; and

FIGURE 3 is an elevational view partially in section illustrating another form of equipment for practicing the invention.

-In FIGURE 1 the equipment for practicing the invention includes the work rollers 1 and 2 mounted to rotate about the axes 3 and 4. As will be more clearly understood hereinafter, the rollers may be freely rotatable or may be driven. The rollers 1 and 2 are formed with identical working surfaces 5 and 6 and guiding surfaces 10 and 11.

Disposed below the rollers 1 and 2 are a plurality of guide rollers 12 respectively mounted to rotate about the axes 13 and 14. Induction heating coils are designated by 15 and 16. A ram is engaged with the cylindrically shaped blank B and exerts a force on the blank in a direction indicated by the arrow 21 or toward the end 22 of the blank.

The equipment of FIGURE 1 is adapted to form the blank B into a tubular geometric form T which, as shown, has an inside and outside diameter greater than the outside diameter of the original blank B.

In carrying out the method the blank B is first formed by conventional techniques. Preferably, the blank is cylindrical in form and has both ends flat and perpendicular to the blank axis A. The blank B is set up on the ram 20 and the end 22 made to engage with the working surfaces 5 and 6 of the rollers. At this time, the equipment is operated to produce relative motion as between the blank B and the rollers 1 and 2, the relative motion taking place about the axis A. The relative motion may be accomplished by rotating the blank and ram 20 with the rollers 1 and 2 freely rotatable or preferably by holding the blank and ram fixed against rotation and rotating the rollers in unison about the axis A. With the latter arrangement, the ram is moved axially to exert pressure.

At this juncture, it is well to comment on the kind of interengagement between the end 22 of the blank and the working surfaces 5 and 6 of the rollers.

The contact between the end of the blank and each of the work surfaces 5 and 6 is a line contact. This is diagrammatically illustrated in FIGURE 3 wherein the line contact between the end 22 of the blank and the roller 5 is indicated by the dotted lines 5a and the line contact is indicated by the dotted lines 6a. It will be noted that each line contact extends from a point closely adjacent the center or the axis A of the blank out towards the periphery. Further, it will be apparent that with relative rotation of the rollers and blank around the axis A the line contacts and 6a will change position and effectively move around the end 22. The path of movement of each line contact is defined by a circle, for example, the circle 23.

When the ram 20 exerts a force on the blank, the working surfaces 5 and 6 provide for forces to develop on the end 22. These forces, of course, are developed in the line contact areas 5a and 6a. These force areas are very small as compared to the total cross sectional area of the blank B. As will be more apparent hereinafter, the concept of exerting working forces on a small area is an important part of the invention.

Turning now to the sequence 'of operations, at the blank B is tightly engaged with the the ram and with relative rotation between the blank and the rollers, the end 22 of the blank will begin to flow radially outwardly, for example, as indicated by the area 24 on the blank. As the material in the area 24 flows outwardly, it is engaged by the guiding surfaces 10 and 11. These surfaces guide the flowing metal back over the outer surface of the blank or as indicated at 25. With further pressure from the ram, the blank continues to extrude radially outwardly and the section indicated by 25 moves back over the surface area occupied by the top-most guide rollers 12. With sustained pressure from the ram, the above-described flowing process continues until such time as the ram has moved down closely adjacent the end 22. At this time, of course, the blank has been completely flowed into a tubular geometric form.

Preferably, the above-described process is carried out with a hot Working operation and the heat is supplied by induction coils such as the coils 15 and 16.

Where tubular form is to be used in a subsequent tube rolling operation, the closed end 22 is cut off. However, where the form is to be used as a cylinder, the end is left intact.

The line contact engagement between the rollers and the end of the blank is an important part of the invention. With the force to cause yield acting over an extremely small area and with the force rapidly rotating around the end of the blank, the actual amount of force necessary to cause yielding is sharply and dramatically reduced. For example, with a four inch diameter blank having a yield strength of sixty thousand pounds, it would be necessary to exert approximately fifty tons on the blank in order to make the same yield if this force were concentrated over the entire end. However, where the force is concentrated in a small line contact area, the total yield force is reduced to approximately one seventh.

The invention contemplates hollow, geometric forms of a character other than tubular, for example, conical and bowl shaped. Equipment for accomplishing the foregoing is illustrated in FIGURE 3.

The rollers and 31 are adapted to rotate about the axes 32 and 33. The rollers are provided with working surfaces 34 and 35 and guiding surfaces 36 and 37. In contact with the working surfaces 34 and 35' are back up rollers indicated at 40 and 41. Just below the guiding surfaces 36 and 37 are the rollers 42 and 43 which respectively rotate about the axes 44 and 45. The rollers 42 and 43 have guiding surfaces 46 and 47. Induction heating coils are indicated at 50 and a ram 51 is in engagement with the blank B-1. The blank is guided by a plurality of rollers one of which is indicated at 52. These rollers 52 rotate about vertical axes.

The working surfaces 34 and 35 engage the end 53 of the blank in a manner described above. Rotation between the blank and the work surfaces 34 and 35 is effected by holding the blank and ram 51 fixed while rotating the rollers 30 and 31 along with the guide rollers 42 and 43 about the axis A-l.

To flow the blank B-l the ram is moved to move up the blank in contact with the working surfaces 34 and 35. With continued ram pressure, end 53 of the blank flows radially outwardly into the channel formed by the guiding surfaces 3%, 37, 46 and 47. These surfaces guide the flowing metal until the same assumes a conical shape. Preferably the rollers 42 and 43 are oriented to accommodate the tapering thickness of the conical form. The flowing of the metal is continued until such time the ram is closely adjacent the working surfaces 34 and 35.

The invention also contemplates the blank B-l be formed into a bowl shape rather than a conical shaped form. In order to do this, the guide surfaces 36, 37, 46 and 47 are modified so that they are formed by curved surfaces of revolution.

I claim:

1. The method of making a hollow geometric form comprising the steps:

forming an elongated, cylindrically-shaped metal blank;

[providing for a first force to develop on the blank in a direction towards one end of the blank; providing for second forces to develop on said one end and in a direction opposite to said first force, the second forces being developed respectively in a pair of line contact areas, each force area extending radially outwardly from adjacent the center of said one end to the periphery of said one end; causing each said line contact area force to move around said one end, each force moving in a path defined by a circle;

causing said first and second forces to cause the portion of the blank adjacent said one end to yield and flow radially outwardly;

engaging said outwardly flowed metal to guide the same back over the outer surface of the blank so that the extrusion assumes a tubular geometric form; and

4 continuing to apply said first and second forces and effecting said guiding until the blank is formed into a tubular geometric form.

2. The method of claim 1 further including the steps of heating the blank and maintaining it in a heated condition while applying said forces and effecting said guiding.

3. The method of making a hollow, geometric form comprising the steps:

forming an elongated, cylindrically-shaped metal blank;

providing for a first force to develop on the blank in a direction towards one end;

providing for second forces to develop on said one end and in a direction opposite to said first force, the second forces being developed respectively in a pair of line contact areas, each force area extending radially outwardly from adjacent the center of said one end to the periphery of said one end;

causing each side line contact area force to move around said one end, each force moving in a path defined by a circle;

causing said first and second forces to cause the portion of the blank adjacent said one end to yield and flow outwardly;

engaging said outward extrusion to guide the same so that the extrusion assumes a conical geometric form; and

continuing to apply said first and second forces and effecting said guiding until the blank is formed into a conical geometric form.

4. The method of claim 3 further including the steps of heating the blank and maintaining it in a heated condition While applying said forces and effecting said guiding.

5. The method of making a hollow, geometric form comprising the steps:

forming an elongated, cylindrically-shaped metal blank;

providing for a first force to develop on the blank in a direction towards one end; providing for second forces to develop on said one end and in a direction opposite to said first force, the second forces being developed respectively in a pair of line contact areas, each force area extending radially outwardly from adjacent the center of said one end to the periphery of said one end; causing each said line contact area force to move around said one end, each force moving in a path defined by a circle;

causing said first and second forces to cause the portion of the blank adjacent said one end to yield and flow outwardly;

engaging said outward extrusion to guide the same so that the extrusion assumes a bowl-shaped geometric form; and

continuing to apply said first and second forces and effecting said guiding until the blank is formed in a bowl-shaped geometric form.

6. The method of making a hollow, geometric form comprising the steps:

forming an elongated metal blank;

providing for a first force to develop on the blank in a direction towards one end;

providing for second forces to develop on said one end and in a direction opposite to said first force, the second forces being developed respectively in a pair of line contact areas, each force area extending radially outwardly from adjacent the center of said one end to the periphery of said one end;

causing each said line contact area force to move around said one end, each force moving in a path defined by a circle;

causing said first and second forces to cause the portion of the blank adjacent said one end to yield and flow outwardly;

engaging said outward extrusion to guide the same so that the extrusion assumes a hollow geometric form; and

References Cited by the Examiner UNITED STATES PATENTS 1/1961 Kaul 72-256 FOREIGN PATENTS 3/ 1953 Germany.

OTHER REFERENCES German patent application (Bosch), 1,000,771, January 1957. CHARLES W. LANHAM, Primary Examiner. H. D. HOINKES, Assistant Examiner. 

1. THE METHOD OF MAKING A HOLLOW GEOMETRIC FORM COMPRISING THE STEPS; FORMING AN ELONGATED, CYLINDRICALLY-SHAPED METAL BLANK; PROVIDING FOR A FIRST FORCE TO DEVELOP ON THE BANK IN A DIRECTION TOWARDS ONE END OF THE BLANK; PROVIDING FOR SECOND FORCES TO DEVELOP ON SAID ONE END AND IN A DIRECTION OPPOSITE TO SAID FIRST FORCE, THE SECOND FORCES BEING DEVELOPED RESPECTIVELY IN A PAIR OF LINE CONTACT AREAS, EACH FORCE AREA EXTENDING RADIALLY OUTWARDLY FROM ADJACENT THE CENTER OF SAID ONE END TO THE PERIPHERY OF SAID ONE END; CAUSING EACH SAID LINE CONTACT AREA FORCE TO MOVE AROUND SAID ONE END, EACH FORCE MOVING IN A PATH DEFINED BY A CIRCLE; CAUSING SAID FIRST AND SECOND FORCES TO CAUSE THE PORTION OF THE BLANK ADJACENT SAID ONE END TO YIELD AND FLOW RADIALLY OUTWARDLY; ENGAGING SAID OUTWARDLY FLOWED METAL TO GUIDE THE SAME BACK OVER THE OUTER SURFACE OF THE BLANK SO THAT THE EXTRUSION ASSUMES A TUBULAR GEOMETRIC FORM; AND CONTINUING TO APPLY SAID FIRST AND SECOND FORCES AND EFFECTING SAID GUIDING UNTIL THE BLANK IS FORMED INTO A TUBULAR GEOMETRIC FORM. 